Refining of animal and vegetable oils



Patented Dec. 4, 1951 REFINING OF ANIMAL AND VEGETABLE OILS Morris Mattikow, New York, N. Y.

No Drawing. Application October 2, 1946, Serial No. 700,830

Claims. 1 This invention relates to the refining of animal and vegetable oils and more particularly, to the refining of such oils while they contain an organic solvent for the oil.

The present invention is particularly adapted to the refining of solvent extracted glyceride oils while they contain at least a portion of the solvent employed for extracting the oil from the natural oil containing materials. The conventional procedure in refining solvent extracted oil is to first remove substantially all of the solvent from the oil and then subject the solvent-free oil to known refining procedures including alkali refining to remove free fatty acids as well as gums and coloring matter. The patent to Thurman No. 2,260,731, however, discloses a process in which the oil is alkali-refined in the presence of a solvent for the oil. This alkali refining may be performed either on a crude oil containing solvent to remove both gums and free fatty acids as well as coloring matter from the oil, or the crude oil may be first subjected to a degumming step after which the oil is alkali-refined in the presence of the solvent.

In accordance with the present invention, it has been discovered that the employment of a ratio of solvent to oil which is below a maximum critical ratio markedly improves the uality of the refined oil resulting from either a partial or complete refining operation in the presence of an oil solvent. The present process has particular utility in connection with the refining of cotton seed oil and other highly colored oil. It will, therefore, be described primarily with respect to cottonseed oil but has utility with substantially all glyceride oils including other vegetable oils such as soya bean or corn oil, as well as animal and fish oils.

Solvent extraction of cottonseed oil has bee suggested and such solvent extraction does remove a greater amount of oil from the seed than conventional processes employing hydraulic presses or expellers. Solvent extraction of cottonseed oil has not, however, been extensively employed commercially. Difiiculty has been encountered in producing a commercially acceptable refined oil from the solvent extracted cottonseed oil. The major difficulty is the inability to produce a refined oil of sufiiciently low color to meet the standards of the cottonseed oil industry. In other words, solvent extracted cottonseed oil contains much more coloring matter than pressed or expelled oil and it has not been heretofore possible to economically remove the excess coloring matter from the oil. Suggested processes involving substantially complete removal of the solvent from the solvent-extracted oil prior to refining have not proved practical since such processes have either required subjecting the oil to elevated temperatures for a sufiicient length of time to set the color in the oil or have required ex pensive and time-consuming solvent stripping operations with steam at low temperature and under high vacuum. The latter type of operation ordinarily results in difficulty resoluble water in oil emulsions requiring additional emulsion breaking steps.

In accordance with the present invention, it has been found that the color can be reduced below that required by the standards of the industry by alkali-refining the cottonseed oil in the presence of the solvent employed to extract the oil so long as the ratio of solvent to oil is maintained below a certain maximum ratio. If this maximum ratio is exceeded, the color is not adequately removed as the solvent holds a portion of the coloring matter in solution in the oil. It has not proved practical to attempt to remove this coloring matter by subsequent bleaching operations.

A greater ratio of solvent to oil than the maximum ratio above referred to also causes an increase in the phosphorous content of the refined oil showing that the gums, including phosphotides, have not been adequately removed in the alkali-refining operation. This is not peculiar to cottonseed oil but occurs with substantially all glyceride oils. A similar action occurs with respect to partial refining or-degumming of glyceride oils in the presence of an oil solvent, for example, in producing a non-break oil. If the ratio of solvent to oil in a degumming operation exceeds a maximum ratio the solvent holds a portion of the gums in solution in the oil, thus resulting in failure to produce a non-breaking oil and reducing recovery of the valuable gums as a by-product. After the gums have been removed in either a degumming or alkali-refining operation, the remaining solvent can be removed from the oil without difiiculty.

It is therefor an object of the present invention to provide an improved process of refining or partially refining glyceride oils in the presence of an oil solvent.

Another object of the invention is to provide a process of refining glyceride oils in the presence of an oil solvent in which the ratio of solvent to an improved process of refining highly colored,

glyceride oils in which the alkali-refining is car- 00 ried out in the 'presence of an oil solvent and the 3, ratio of solvent to oil is made sufficiently low to remove a major portion of the coloring matter.

Other objects and advantages of the invention will be apparent from the following description of preferred embodiments thereof.

The Thurman patent, supra, discloses apparatus suitable for carrying out the present invention and may be referred to for detailed disclosure of such apparatus and process steps as are not described in detail in the present application.

A solvent extracted oil will ordinarily contain at least as much solvent as oil by weight. That is to say, the weight ratio of solvent to oil will ordinarily range from approximately 1 to 1 to to 1. In accordance with the present invention, it has been found that for either a degumming operation or an alkali-refining operation, this ratio of solvent to oil must be reduced below a critical maximum ratio. For degumming operations, it has been found that this maximum ratio is approximately 1 to 4, i. e., the oil should contain not greater than approximately 25% solvent based on the weight of the oil and for an alkali-refinin operation, this ratio should be not greater than approximately 33% solvent based on the weight of the oil. The critical maximum ratios of oil to solvent will vary somewhat with different oils and different solvents therefor, but for any given oil and solvent mixture effective refining treatment cannot be accomplished if the ratio exceeds a critical value which is always close to those above given.

The excess solvent can be removed from solvent extracted oil by any suitable low temperature distillation process, for example, the flash distillation step of the Thurman patent, supra. It is desirable to vaporize the excess solvent from the oil at a relatively low temperature, for example, a temperature below 150 and this isparti uarly true of highly colored oils, such as cottonseed oil. Somewhat higher temperatures, for example, temperatures as high as 220 F., can be employed in flash distillation operations in which the oil is maintained at a high temperature for a short period of time, for example, not in excess of minutes, while for other types of distillation op erations, requiring a longer length of time, temperatures below 150 F. are preferred. The setting of the color in the oil is a function of both time and temperature, such that the higher the temperature, the shorter the period of time at which the oil can be maintained at the high temperature.

By reducing the solvent to below approximately of the oil, the gums, including the phosphatides, can be substantially completely removed from the oil by a degumming step such as described in the Thurman patent, supra. In such a step, an aqueous precipitating agent is thoroughly admixed with the oil and solvent mixture. The precipitating agent may be water alone or a solution of substantially any electrolyte either acidic, neutral or basic. If substantially neutral salts or other electrolytes which do not attack the oil or the gums, such as weak acids or bases, are employed, the solution may be relative- 1y concentrated while for strong acids or bases diluate solutions may be used. The precipitating agent may also contain water-miscible solvents such as alcohols which are substantially immiscible with the oil and extraction solvent at the temperature of the degumming operation. The amount of precipitating agent will usually range between 1% and 10% on the basis of the oil solvent mixture, best results being ordinarily obtained with from 5% to 6% of precipitating agent. The resulting foots including the precipitated gums can be separated from the oil solvent mixture in any desired manner, such as settling, or decantation, although continuous centrifugal separation produces the best results and is preferably preceded by a continuous mixing step for admixing the agent with the oil.

The temperature during mixing of the oil with the degumming reagent and the temperature during separation will vary with the oil being treated. A mixing temperature of approximately 70 F. will ordinarily be employed but this temperature may vary from approximately 70 F. to a temperature just below the boiling point of the solvent. Separation temperatures will also vary in the above range but will ordinarily be in the neighborhood of to F. The temperatures for both mixing and separation may sometimes be advantageously increased up to approximately to F. by operating under pressure, and with some oils it is advantageous to mix at such higher temperatures and then cool to a lower temperature for separation.

An alkali-refining operation either after a preliminary degumming operation such as just described, or upon the crude oil solvent mixture, requires that the solvent be reduced below approximately 33% of the oil. Such an alkalirefining operation involves the admixture of an aqueous solution of an alkali with the oil to cause the alkali to react with the free fatty acids of the oil to form soapstock which may be separated from the oil-solvent mixture in any known suitable manner, such as settling, decanting, or filtration, although the preferred separation step is by continuous centrifugal separation. Thus, the mixing of the alkali solution with the oil-solvent mixture may be carried out continuously, as described in the Thurman patent, supra, and the separation also accomplished by continuous centrifugal separation, as also. described in the Thurman patent. In general, a caustic alkali, such as caustic soda or caustic potash is. necessary for color removal in the alkali-refining step. The amounts and concentrations of the alkali solution vary with the nature of the oil, and the correct amounts and. concentrations are known to the prior art. Thatis to say, the refiner. determines the free fatty acid content of the oil, calculates the equivalent amount of alkali, and

adds the alkali in the. form ofan aqueous solution of the proper concentration as determined by, experience and publications known to the art and in an amountproviding a predetermined excess over that required toneutralize the free fatty acids. The mixing and separation temperatures will besimilar to those discussed above with respect to a degumming operation.

In general, the amount of solvent present in the crude oil or partially refined oil during the degumming or alkali-refining operation of the present invention will be approximately 25%. Removal of solvent, down to 25%, is relatively easily accomplished and in fact, no difiiculty is encounteredin reducing the amount of solvent to between 5% and 10% of theoil by low temperature distillation. The removal of the remaining 5% to 10% of the solvent does, however, present difiiculties. Either the temperature or distillation must be increased sufiiciently to deleteriously affect the quality of the oil by modifi-,

cationcf heat-sensitive impurities or a low-temperature steam distillation step under high vacuum must be employed. In thelatter case,

in the oil.

range of solvent content in the oil contemplated by the present invention where separate degumming and alkali-refining steps are performed will, therefore, ordinarily be between approximately 5% and 25%, although if alkali-refining even in the presence of gums is to be carried out, this range may be from approximately 5% to 33%. After the ums have been removed from the oil, either through a partial or complete refining operation, the remaining solvent is easily removed. In cases where a light colored oil is required from a highly colored oil, such as cottonseed oil, the removal of the excess coloring matter by alkalirefining in the presence of a proper amount of solvent also enables the remaining solvent to be easily removed without danger of setting the color While the solvent may be substantially completely removed from the oil prior to the usual bleaching operation on colored oils which have been alkali-refined, it is possible to perform the bleaching operation in accordance with the present invention while the oil still contains 25% to 35% solvent. Such a bleaching operation ordinarily involves the addition of a finely divided adsorbent, such as activated clay, carbon black, etc. This is followed by a filtering operation in which the adsorbent containing adsorbed coloring material is filtered from the oil. By bleaching the oil while it still contains solvent, the final solvent removal step may be combined with a deodorizing step which usually involves steam distillation of the oil at high temperatures under a low vacuum. That is to say, the solvent may be vaporized from the oil in an initial portion of the deodorizing operation and condensed along with water. As the solvent is ordinarily immiscible with water, it may be easily separated from the water and returned to the solvent extraction operation.

The process as described above is applicable to oils extracted with any of the usual oil solvents employed in solvent extraction processes. The ordinarily used solvent is commercial hexane which is a mixture of hydrocarbons including hexanes and boils in the hexane range. For example, one commercial hexane is a water-white material having a specific gravity of 74.4 A. P. I. at 60 F., a boiling point range of 140 to 160 F., and a vapor pressure at 100 F. of 5.1 lbs. per square inch. Other oil solvents, for example, pure hexane, benzene, gasoline, petroleum ether, dichloroethylene, trichloroethylene, heptane, pentane, etc., may be employed. Also, propane or similar solvents which are normally gaseous but which may be liquified under pressure, may be employed if the process is carried out under pressure. In any event, it is preferred to carry out the process in a system which is substantially closed from the atmosphere to prevent loss of solvent.

As an example showing the results to be expected in operations in accordance with the present invention, a crude cottonseed oil havin a free fatty acid content and containing 33.4% of petroleum ether based on the weight of the oil was refined with 20 B. caustic soda in an amount providing an 0.5 excess. The color of the refined oil was 35 yellow-5.7 red (Lovibond Tintometer, 5% column). Another portion of the same oil was refined under the same condi tions in the presence of 100% solvent. The color was 35 ye1low-81 red (Lovibond Tintometer, 1

inch column converted to a 5%." column). The first refined oil bleached readily while the second oil could not be bleached economically.

As another example, a crude cottonseed oil having a phosphatide content of 1.51% was sub jected to a degumming operation with 6% water while the oil contained 19.6% petroleum ether. The degummed oil had a phosphatide content of 0.46%. Another portion of the same oil was treated under the same conditions with the sameamount of water while the oil contained 38.1% of petroleum ether. Substantially no gums were precipitated and the resulting oil had substantially the same phosphatide content as the crude oil.

Similarly, a crude soya bean oil having a phosphatide content of 1.98% and containing 23.5% petroleum ether Was degummed with 6% water and the resulting oil had a phosphatide content of 0.40%. Another portion of the same oil containing 32.9% petroleum either was treated in the same manner. The phosphatide content of the resulting oil was the same as that of the crude oil.

From the above description of the invention, it is apparent that I have provided an improved process particularly adaptable to treating highly colored oils such as cottonseed oil and which produces a low colored oil in an economical process. Thus, solvent extracted cottonseed oil can be readily reduced in color by alkali-refining in the presence of a limited amount of solvent to below 35 yellow and 7.6 red on a 5 column in a Lovibond Tintometer, and such oil can be readily bleached to below 20 yellow and 2.5 red. Thus, by a proper ratio of oil solvent to the oil in an alkali-refining process, heat-sensitive color bodies can be removed before they are subjected to sufficient time and temperature treatment in a solvent removal step to modify these bodies rendering them incapable of economical removal from the oil, In all glyceride oils, a proper ratio of oil solvent to oil also enables substantially all of the gums, including the phosphatides, to be removed from the oil either in a degumming oper ation or in an alkali-refining operation.

While I have disclosed the preferred embodiments of my invention, it is understood that the details thereof may be varied within the scope of the following claims.

I claim:

1. The process of refining a crude glyceride oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil, which comprises, mixing an aqueous refining agent with said oil while said oil is in admixture with between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture impurities precipitated therein by said refining agent, and thereafter vaporizing said solvent from said oil.

2. The process of partially refining crude glyceride oil, which comprises, mixing an aqueous degumming agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said oil is in admixture with between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture impurities precipitated therein by said degumming agent, and thereafter vaporizing said solvent from said oil.

3 The process of refining a crude glyceride oil, which comprises, mixing an aqueous alkali refining agent with said oil to precipitate impurities in said oil Without substantial attack upon the glycerides of said oil while said oil is in admixture with between approximately 5% and 33% of volatile organic solvent for said oil based on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture soapstock precipitated therein by said agent, and thereafter vaporizing said solvent from said oil.

4. The process of refining a crude cottonseed oil, which comprises, mixing an aqueous caustic alkali refining agent with said oil to precipitate impurities in said oil Without substantial attack upon the glycerides of said oil while said oil is in admixture with between approximately 5% and 33% of volatile organic solvent for said oil based on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture soapstock including coloring matter precipitated therein by said agent, and thereafter vaporizing said solvent from said oil.

5. The process of refining a crude glyceride oil, which comprises mixing an aqueous degumming agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said oil is in admixture with between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil, continuously centriiugally separating from the oil and solvent mixture impurities precipitated therein by said degumming agent, thereafter adding an aqueous alkali refining agent to the resulting oil and solvent mixture to precipitate additional impurities in said oil'without substantial attack upon the glycerides of said oil, continuously centrifugally separating from said resulting oil and solvent mixture soapi.

stock precipitated therein by said alkali refining agent, and thereafter vaporizing said solvent from said oil.

6. The process of refining a crude 'glyceride oil, which comprise mixing a stream of aqueous refining agent with a stream of oil-solvent mixture containing between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil, delivering the resulting stream to 'a continuous centrifugal separator, and continuously separating from said oil and solvent mixture in said centrifugal separator, impurities precipitated in said oil and solvent mixture by said refining agent and thereafter vaporizing the remaining solvent from said oil.

'7. The process of refining 'a crude glycerideoil, which comprises, mixing a stream of aqueous degumming agent with a stream of oil-solvent mixture containing between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil, delivering the re sulting stream to a continuous centrifugal separator, and continuously separating from said oil and solvent mixture in said centrifugal separator, impurities precipitated in said oil and solvent mixture by said degumming agent and thereafter vaporizing the remaining solvent fromsaid oil.

8. The process of refining a crude glyceride oil, which comprises, mixing a stream of aqueous alkali refining agent with a stream of oil-solvent mixture containing between approximately 5% and 33% of volatile organic solvent for said oil based on the weight of said oil to precipitate impurities in said oil Without substantial attack upon the gly-ceride of said oil, delivering the resulting stream to a continuous centrifugal separator, and continuously separating from said oil and solvent mixture in said centrifugal separator, soapstock precipitated in said oil and solvent mixture by said refining agent and thereafter vaporizing the remaining solvent from said oil.

9. The method of refining a solvent extracted crude glyceride oil containing a volatile organic solvent for said oil, which comprises, vaporizing a portion of said solvent from the miscella r sulting from a solvent extraction step to reduce the solvent content of the oil below approximately 25% but not less than approximately 5% based on the weight of the oil, mixing an aqueous refining agent with the resulting oil and solvent mixture to precipitate impurities in said oil without substantial attack upon the glycerides of said oil, continuously centrifugally separating from the oil and solvent mixture impurities precipitated therein by said refining agent, adding a finely divided adsorbent to the resulting oil and solvent mixture to bleach said oil, filtering said adsorbent from said resulting oil and solvent mixture and thereafter subjecting said resulting oil and solvent mixture to steam deodorization under vacuum conditions to vaporize said solvent from said oil and deodorize said oil.

10. The method of refining a solvent extracted glyceride oil containing a volatile organic solvent for said oil, which comprises, vaporizing a portion of said solvent from the miscella resulting from a solvent extraction step for said oil to reduce the solvent content of said oil below approximately 33% but not less than approximately 5% based on the weightof said oil, mixing an aqueous alkali refining agent with the resulting oil and solvent mixture to precipitate impurities in said oil Without substantial attack upon the glycerides of said oil, continuously centrifugally separating from the oil and solvent mixture soapstock precipitated therein by said refining agent, adding a finely devided adsorbent to the resulting oil and solvent mixture to bleach said oil, filtering said adsorbent from said resulting oil and solvent mixture and thereafter subjecting said resulting oil and solvent mixture to steam deodorization under vacuum conditions to vaporize said solvent The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,408,804 Gleitz Mar. '7, 1922 2,260,731 Thurman Oct. 28, 1941 2,288,441 Ewing June 30, 1942 2,380,412 Buxton July 31, 1945 2,380,413 Burton July 31, 1945 FOREIGN PATENTS Number Country Date 308,250 Great Britain Mar, 6, 1930 

1. THE PROCESS OF REFINING A CRUDE GLYCERIDDE OIL TO PRECIPITATE IMPURITIES IN SAID OIL WITHOUT SUBSTANTIAL ATTACK UPON THE GLYCERIDES OF SAID OIL, WHICH COMPRISES, MIXING AN AQUEOUS REFINING AGENT WITH SAID OIL WHILE SAID OIL IS IN ADMIXTURE WITH BETWEEN APPROXIMATELY 5% AND 25% OF VOLATILE ORGANIC SOLVENT FOR SAID OIL BASED ON THE WEIGHT OF SAID OIL, CONTINUOUSLY CENTRIFUGALLY SEPARATING FROM THE OIL AND SOLVENT MIXING IMPURITIES PRECIPITATED THEREIN BY SAID REFINING AGENT, AND THEREAFTER VAPORIZING SAID SOLVENT FROM SAID OIL. 